In recent years, several types of microfluidic devices have been developed for e.g. biochemical processing, biochemical synthesis, and/or biochemical detection. For example, U.S. Pat. No. 6,632,655 B1 describes several types of microfluidic devices which can e.g. be used for biochemical analysis.
According to one type of such micro fluidic devices which is for instance suited for sequencing-by-synthesis, magnetic particles are subsequently driven or actuated through a plurality of chambers, wherein e.g. a plurality of different physical, chemical, or biochemical processes is performed in the plurality of chambers. The magnetic particles may for instance be provided with a (biological) component to be analyzed. In this type of microfluidic device, several chambers through which the magnetic particles are subsequently moved are connected by channels defining a flow path for the magnetic particles. The plurality of chambers and the interconnecting channels define a processing module. Since different fluids may be provided in the plurality of chambers, valve-like structures are typically provided in the channels connecting the chambers. These valve-like structures are adapted for enabling passing-through of the magnetic particles and prevent (at least substantially) mixing of the fluids present in the different chambers. For example, such valve-like structures may contain a visco-elastic medium through which the magnetic particles can travel. The magnetic particles are actuated through the plurality of chambers by means of an applied magnetic field (or several applied magnetic fields) generated by a magnetic-field generating unit. In such a system, the dynamics of magnetic particles such as the traveling speed, the position in the micro fluidic device at a predetermined time after the start of a process, and/or the residence time in the respective components of the micro fluidic device may deviate from an ideal (or planned) behavior due to e.g. manufacturing tolerances. For example, the magnetic particles, e.g. formed by magnetic beads, may show varying properties such as varying susceptibility, size, or surface coating. Further, the valve-like structures separating the plurality of chambers may have varying properties such as varying roughness, surface tension, or size. As another reason for deviations in the dynamics of the magnetic particles, the magnetic field for actuating the magnetic particles through the microfluidic device may comprise spatial non-uniformities.
In many cases, microfluidic devices for high-throughput and/or high-multiplex applications are desired. In such devices, processing should be performed simultaneously in a plurality of (substantially) identical processing modules in parallel. For example, FIG. 1 schematically shows a micro fluidic device comprising a plurality N of parallel processing modules (with N=3 in the example). The number N of modules can be very high, e.g. 5, 10, 1000, 105 or even much higher. Since devices of compact size are preferred, microfluidic devices comprising a high number of modules shall be provided in a miniaturized way. However, for a high number of modules and efficient miniaturization, it becomes difficult to miniaturize individual magnetic-field generating units for the respective processing modules. As a consequence, shared magnetic-field generating units provided for a plurality of processing modules (or even one magnetic-field generating unit provided for all processing modules) are preferred for actuating the magnetic particles in the respective processing modules. However, the implementation of such shared magnetic-field generating units has the drawback that the transport speed, positions in the respective processing modules, residence time, and the like cannot be independently controlled for the individual processing modules. Due to the manufacturing tolerances described above, as a consequence the magnetic particles in different processing modules may become de-synchronized, i.e. may travel at different speed, may be located at different positions at a given moment in time, and/or may comprise different residence time in the components of the micro fluidic device. This de-synchronization may result in different or non-ideal chemical, biochemical, or physical processes in the chambers which is undesirable.